Kenyan MPs have passed a law which may make it impossible to prosecute corrupt politicians implicated in the Goldenberg and Anglo Leasing scams, where huge sums were diverted to the back pockets of government officials.

The new law limits Kenya's Anti-Corruption Commission to investigate alleged crimes committed only after 2003.

The Goldenberg and Anglo Leasing cases predate the cut-off date.

President Mwai Kibaki won polls in 2002 on an anti-graft platform he has yet to fulfil. He faces re-election this year.

Observers say the new law may have been timed to ensure no politicians face damaging legal proceedings ahead of the polls.